The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Cameras or scanning units having a lighting unit are used for the optical taking or scanning of bodies. The intensity of the lighting unit is matched to the requirements of the camera and/or of the application. A scanning unit includes a lighting unit and a light receiver unit such as is described, for example, in U.S. Pat. No. 6,628,445 B2.
6-side readings are used today, for example, for the reading of a barcode. The light beams of four side cameras or scanning units run at an angle (for example of 45°) to the conveying direction of a transport belt on which a body is guided through the reading zone. It is ensured by the oblique alignment of the four side cameras that each side of the body can be imaged irrespective of the position of the body. Cameras or scanning units are likewise provided for the upper and lower sides of the body.
It has to be avoided that the lighting units of the individual scanning units mutually influence one another. It should in particular be avoided that a multiple exposure of the zone to be scanned by a plurality of scanning units arises. In known solutions, this is precluded by the spatial separation of the light beams generated by the lighting units of the individual scanning units within the reading field, as is shown in FIGS. 11 and 12. FIG. 11 shows, in a schematic and perspective representation, the arrangement of a 6-side solution for the identification of a barcode on the surface of a body 10 which is guided through the reading device on the conveying device 12. Six scanning units 104, 108, 112, 116, 120, 124 each include a lighting unit which transmit light in the direction of a reading field and which can be formed e.g. by LED arrays, see U.S. Pat. No. 6,628,445 B2. The scanning units moreover each include a light receiver unit which can possibly receive light reflected by the body. It comprises, for example, an array of CMOS or CCD sensors. In this manner, the scanning units 104 to 124 define scanning zones 106, 110, 114, 118, 122 and 126 which are indicated in bar shape and which are aligned such that every surface of the body can be scanned. Two of the side surfaces to be scanned are designated by reference numerals 82 and 84 in FIG. 11. The upper surface to be scanned by the scanning unit 120 is designated by reference numeral 88. The scanning zone 126 of the lower scanning unit 124 extends in the example shown through an interruption 130 of the conveying device 12.
It is shown in FIG. 12 how in particular the four side scanning units 104, 108, 112, 116 are arranged such that the light beams of the individual lighting units do not overlap in the reading field 134. The reading field must have a corresponding length for this purpose. Due to the spatial separation of the light beams, a correspondingly large mechanical system design is required for the scanning which extends over a long region of the transport surface or technical conveying device. High demands must therefore be made on the consistency of the conditions in the large reading field. In particular when a plurality of conveyor belt segments are present, the speeds of the individual segments must be synchronized such that they run at the same speed, which makes very high demands on the system design. This is in particular hardly practical when the weight of the individual bodes has an influence on the transport belt speed of individual segments.
Independently of this, the prevention of over-exposure, for example by reflections or glare at the surface of the body to be scanned, or of a deterioration of the image quality resulting therefrom is desired.
In a generic scanning method for the optical scanning of at least one part surface of a body, the body is illuminated by at least one lighting unit. At least one light receiver unit can receive light which is transmitted onto the body by the lighting unit and is reflected by the body. The lighting unit and the light receiver unit defining a scanning zone of a scanning unit including the lighting unit and the light receiver unit. A generic scanning apparatus for the carrying out of such a method has at least one lighting unit for the illumination of at least a part of a reading field, at least one light receiver unit for the reception of light which may be reflected from the reading field and for the generation of a received signal and an evaluation unit for the evaluation of the received signal. A scanning zone of a scanning unit is defined by the light path from the lighting unit to the light receiver unit.